Field of the Invention
The invention relates to a photoelectric sensor and a control method of the photoelectric sensor, and particularly relates to a photoelectric sensor capable of saving energy and a control method of the photoelectric sensor.
Description of Related Art
Generally, a photoelectric sensor applies an oscillation circuit to produce a light projecting pulse to periodically drive a light projecting element, and in an object detection region, a detected object blocks or reflects the light coming from the light projecting element, and a light receiving element cannot receive the light from the light projecting element or the light receiving element receives the light from the light projecting element to generate a light signal, and determines whether the detected object exists based on the light signal.
In the photoelectric sensor, a pulse generated by the oscillation circuit is generally a pulse with a fixed pulse width and fixed period. However, in recent years, the idea of energy saving draws more attention.
In order to achieve the effect of energy saving, a patent literature 1 (Japan patent No. 6-209250) discloses a photoelectric switch. In the photoelectric switch of the patent literature 1, an oscillation circuit used for producing the light projecting pulse is connected to a start detection circuit, where the start detection circuit is used for determining whether an environment where the photoelectric switch is located is suitable for detecting an object and a human body, etc. In case that the start detection circuit determines that the current environment is not suitable for the photoelectric switch to implement detection, the oscillation circuit produces a long first period T1, and in case that the start detection circuit determines that the current environment is suitable to implement the detection, the oscillation circuit produces a second period T2 shorter than the first period T1. In this way, by setting two different pulse periods, during the long first period T1, the energy consumed by a light-emitting device is decreased, so as to save the energy.
A patent literature 2 (U.S. Pat. No. 5,331,150A) discloses another photoelectric switch. In the photoelectric sensor, when a state of an optical path is changed, the oscillation circuit is changed from a state of producing the pulse with a long period to a state of producing the pulse with a short period, so as to achieve the effect of energy saving.
Moreover, an interference signal is a main reason causing a detection error of the photoelectric sensor, so that it is important to improve an anti-interference performance of the photoelectric sensor.
However, in the aforementioned patent literatures, there is no content related to anti-interference technique.                Patent literature 1: Japan patent No. 6-209250        Patent literature 2: U.S. Pat. No. 5,331,150A        